Translated Abstract
Space charges will be formed in a polymer when high voltage is applied on it. The space charges could distort the electric field seriously and lead to the high local field and finally the breakdown of the sample. Because the formation of space charges in the polymer is associated with the morphology of the polymer tight, we blended the LDPE with LLDPE which have a good compatibility. PEA and DSC methods were used to measure the distribution of space charge and the crystalline in samples respectively. It is concluded after the analysis of the mechanism of space charge formation that the polymer blend has higher crystallinity than LDPE. There is partial co-crystallization in the blend. Finally, we found LDPE blend by 60 wt % LLDPE blend is the best for depression of space charge.The injection and extraction of electrons lead to initiation of electrical treeing, then results in the occurrence of breakdown finally. A high-permittivity material, namely charge barrier layer, was sandwiched between the electrode and polymer dielectrics to suppress the injection of carriers. In this paper, three types of barrier layers with different permittivity were selected to study the influence on the formation of space charge. The results show that PVDF with the higher permittivity of 6.4, can suppress the injection of electron, whereas its strong polarization can result in the accumulation of the space charges in the dielectrics Polyimide added by nano-material with the proper permittivity of 4 can effectively suppress the injection of the electron and hole.
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